Field of the Invention
This invention relates generally to touch sensors, near field communication technology such as NFC technology that is found in contactless smart cards, and a display. More specifically, the present invention physically and logically combines near field communication technology, touch sensor technology and display technology by using a more powerful near field communication antenna disposed under or around a perimeter of the touch sensor and display screen for transmitting, and a smaller near field communication antenna under or on top of the touch sensor for receiving near field communication signals. The system may also enable the shared use of certain components for the purposes of each of these functions, thereby offering increased security from attack by more closely integrating the physical and logical operations while offering simultaneous and independent operation of each.
Description of Related Art
There are several designs for capacitance sensitive touchpads. It is useful to examine the underlying technology to better understand how any capacitance sensitive touchpad can be modified to work with the present invention.
The CIRQUE® Corporation touchpad is a mutual capacitance-sensing device and an example is illustrated as a block diagram in FIG. 1. In this touchpad 10, a grid of X (12) and Y (14) electrodes and a sense electrode 16 is used to define the touch-sensitive area 18 of the touchpad. Typically, the touchpad 10 is a rectangular grid of approximately 16 by 12 electrodes, or 8 by 6 electrodes when there are space constraints. Interlaced with these X (12) and Y (14) (or row and column) electrodes is a single sense electrode 16. All position measurements are made through the sense electrode 16.
The CIRQUE® Corporation touchpad 10 measures an imbalance in electrical charge on the sense line 16. When no pointing object is on or in proximity to the touchpad 10, the touchpad circuitry 20 is in a balanced state, and there is no charge imbalance on the sense line 16. When a pointing object creates imbalance because of capacitive coupling when the object approaches or touches a touch surface (the sensing area 18 of the touchpad 10), a change in capacitance occurs on the electrodes 12, 14. What is measured is the change in capacitance, but not the absolute capacitance value on the electrodes 12, 14. The touchpad 10 determines the change in capacitance by measuring the amount of charge that must be injected onto the sense line 16 to reestablish or regain balance of charge on the sense line.
The system above is utilized to determine the position of a finger on or in proximity to a touchpad 10 as follows. This example describes row electrodes 12, and is repeated in the same manner for the column electrodes 14. The values obtained from the row and column electrode measurements determine an intersection which is the centroid of the pointing object on or in proximity to the touchpad 10.
In the first step, a first set of row electrodes 12 are driven with a first signal from P, N generator 22, and a different but adjacent second set of row electrodes are driven with a second signal from the P, N generator. The touchpad circuitry 20 obtains a value from the sense line 16 using a mutual capacitance measuring device 26 that indicates which row electrode is closest to the pointing object. However, the touchpad circuitry 20 under the control of some microcontroller 28 cannot yet determine on which side of the row electrode the pointing object is located, nor can the touchpad circuitry 20 determine just how far the pointing object is located away from the electrode. Thus, the system shifts by one electrode the group of electrodes 12 to be driven. In other words, the electrode on one side of the group is added, while the electrode on the opposite side of the group is no longer driven. The new group is then driven by the P, N generator 22 and a second measurement of the sense line 16 is taken.
From these two measurements, it is possible to determine on which side of the row electrode the pointing object is located, and how far away. Using an equation that compares the magnitude of the two signals measured then performs pointing object position determination.
The sensitivity or resolution of the CIRQUE® Corporation touchpad is much higher than the 16 by 12 grid of row and column electrodes implies. The resolution is typically on the order of 960 counts per inch, or greater. The exact resolution is determined by the sensitivity of the components, the spacing between the electrodes 12, 14 on the same rows and columns, and other factors that are not material to the present invention.
The process above is repeated for the Y or column electrodes 14 using a P, N generator 24
Although the CIRQUE® touchpad described above uses a grid of X and Y electrodes 12, 14 and a separate and single sense electrode 16, the sense electrode can actually be the X or Y electrodes 12, 14 by using multiplexing.
Previously patented technology describes two-factor or three-factor user authentication methods such as described in U.S. Pat. No. 7,306,144 (the 144 patent), wherein using a debit ATM card or accessing protected information or a secure location, it is often desirable to integrate the function of verifying the identity of the user. Verifying identity using a two-factor system may be accomplished using (1) something the user has, such as an account number and one time password generated inside of a contactless card or cell phone, and (2) something that only the user knows, such as a secret PIN/password. Verifying using a three-factor system provides an additional layer of security by adding (3) some user biometric such as a user's fingerprint.
Responding to this desire, the 144 patent was obtained which integrated a contactless card reader touch screen and the biometric contactless touchpad to provide the ability to the payment industry to create applications such as near field communication (NFC) enabled touch screen PIN entry devices and NFC enabled laptop computers for the networking industry. These devices may be used to create secure VPN login devices to give access to remote business networks, and for the physical security industry to create secure token entry devices, such as for building access. The NFC capabilities include contactless card reader functions that enable the reading of data on a smart card, smart phone or other device that may store data that can be read using wireless communication such as through NFC.
In the 144 patent, the integrated contactless card reader is integrated into the hardware of a touchpad, wherein the circuit board substrate of the touchpad provides a mechanical substrate on which the hardware of the contactless card reader can be disposed, and wherein the touchpad is already widely distributed in other electronic appliances and as a stand-alone device.
The 144 patent describes “a contactless smart card reader that is integrated into the hardware of a touchpad, wherein the circuit board substrate of the touchpad provides a mechanical substrate on which the hardware of the contactless smart card reader can be disposed, and wherein the touchpad is already widely distributed in other electronic appliances, and as a stand-alone device . . . . Such electronic appliances that incorporate a touchpad include many portable electronic appliances such as laptop computers, personal digital assistants (PDAs), mobile telephones, digital cameras, digital camcorders, etc.” . . . The Cirque® GLIDEPOINT® technology is also integrated into devices that are not designed to be mobile, such as point-of-sale input devices. For example, when a user provides a credit card or a debit card to a cashier for a purchase, it is common to see a dumb card reader that enables the credit or debit card to be swiped in order to read a magnetic strip. The user then typically uses a pen that is coupled to the dumb card reader and either enters a signature or a debit card number. Thus, the CIRQUE® GLIDEPOINT® technology is capable of receiving diverse forms of user input.”
An example of an integrated contactless touchpad is constructed by placing a wire loop antenna or copper traces around the touch sensor. The drawback to this design is that many of the physical structures of the touchpad sensors and the contactless card reader interfere mechanically with each other, as well as electrically.
In an example of a mechanical problem, the touchpad sensor is often too large to support placement of an appropriately sized contactless card reader antenna due to constraints of the standards for contactless card reader operative volume, thereby limiting the practical size of an integrated system.
In an example of an interference problem, the strong magnetic field necessary to power the contactless card reader creates strong eddy currents within the touchpad sensor, thereby causing operation outside of specifications, and malfunctions or inoperability is the result.
In a related interference problem, the touchpad creates strong electrostatic fields that are necessary to detect a finger. These strong fields often cause the contactless card reader to have insufficient signal integrity.
The adverse effects of both the electrostatic fields and magnetic interference is often a result of 1) the contactless card reader signal causing non-linear effects due to noise/interference signal levels being large enough to trigger ESD diodes in touchpad circuitry, 2) difficulty for the touchpad front-end electronics or analog-to-digital converters (ADCs) in tracking the interference also causing non-linear effects and error in measurement, and 3) the amplitude modulation frequency of NFC is often very close to the touch sensing stimulus frequency, thereby creating in-band ground bounce.
Accordingly, what is needed are new techniques for physically combining the area of operation of NFC technology and a touch sensor that will enable integration of an appropriately sized NFC antenna near the touch sensor that accommodates the physical interference of components, especially when using different materials such as ITO and copper traces.
It would be a further advantage to dispose the circuitry of these systems near enough to each other to prevent eavesdropping or tapping into the signals between them to thereby provide an integrated system that is more secure than existing integrated systems. It would be an advantage to provide new techniques that will remove the electrical and magnetic interaction between the two systems of a contactless card reader and a touchpad. It would also be of benefit to integrate the electronics into a single package to address the very limited space of the touchpad and associated routing space typical of today's small and portable electronic appliances. It is also important to control an operating or active volume because of limitations of standards that control operation of an NFC antenna.